A photolithography process of semiconductor device uses a system incorporating a coating-developing apparatus in an exposure apparatus. As an exposure apparatus, a stepper (reduction projection step and repeat exposure system) using KrF excimer laser as a light source is generally used. A stepper applies light to a resist film through a photo mask (reticle), and transfers a predetermined circuit pattern to a resist film. However, in the recent semiconductor device manufacturing, many different types of products are manufactured, and a photo mask must to be made for each type of product in an exposure apparatus, increasing the manufacturing cost. Therefore, electron beam writing exposure requiring no photo mask has received attention.
Electron beam writing exposure is a technique of writing a predetermined pattern by applying an electron beam directly to a resist film. For example, as shown in FIG. 1, an electron beam emitted from an electron gun 111 is bent by an electric field formed by electromagnetic lenses 112 and 113 corresponding to a mask, and a predetermined mark pattern is formed by combination of electromagnetic lenses 112 and 113, and directly written on a resist film 114.
In electron beam writing exposure, an electron beam is easier to be bent if its energy is smaller, and an electron beam with a low acceleration is used. Thus, energy of an electron beam per unit time given to the resist film 114 is small, and if an electro beam is emitted for a short time, the resist film 114 is insufficiently exposed. Particularly, when a chemically amplified resist is exposed by electron beam writing exposure, the amount of exposure is extremely insufficient. If the electron beam emitting time is set long (e.g. about 20 minutes) as a measure to prevent insufficient exposure, a throughput will be lowered.
FIGS. 2A and 2B are schematic illustrations showing exposing and developing states by using a positive chemically amplified resist. First, expose a film coated with the resist 114 on a wafer W. A proton (H+) 116 is generated in an exposure area 115 (shown shaded) as shown in FIG. 2A. Then, heat the wafer W to a temperature of 90-140° C. in a PEB (Post Exposure Bake) process, the proton (H+) diffuses in the resist 114, and accelerates acid catalysis. The proton (H+) resolves a base resin of the resist 114, and the resist 114 becomes soluble in a developing solution. During the acid catalysis, a new proton (H+) is generated like a chain reaction, and the new proton (H+) resolves the base resin. In this way the acid catalysis is amplified and accelerated one after another. Then, pour a developing solution on the resist R coated film. An exposed portion 115 is dissolved, and a resist pattern 115a is formed.
However, in electron beam writing exposure, the exposing amount is insufficient and the exposed portion 115 is difficult to be dissolved in the developing solution, and as shown in FIG. 2B, the resist pattern 115a may become unclear. As a result, it is impossible to form a well-shaped resist pattern with precise line width.
As described above, in electron beam writing exposure, the effective sensitivity of a chemically amplified resist is low and the exposure time is long, and the throughput is extremely lower than exposure by a stepper (reduction projection step and repeat exposure system) using KrF excimer laser (λ=248 nm) or ArF excimer laser (λ=193 nm)